1. Field of the Invention
The invention relates, in general, to bobbins upon which electrical coils are wound for the purpose of providing an inductor or a transformer as the case may be.
More particularly, the invention is directed to a bobbin construction in the form of a molded frame member which is intended to incorporate ferromagnetic laminations in addition to windings placed over the bobbin.
2. Description of the Prior Art
Bobbins, in a great variety of forms, have been described for the purpose of retaining a winding, as well as for housing laminations.
In one example, as seen in U.S. Pat. No. 2,249,057, the component elements include a core and flanges with an inwardly recessed central portion to fit over the core. When these parts are assembled, a bridge member is utilized to hold the flanges together. This type of structure requires hand assembly which is not only time consuming but involves labor costs as well.
In U.S. Pat. No. 2,899,655, the bobbin is of molded plastic and space is provided therewithin to be filled up with laminations. This structure has the disadvantage that the core is only held by frictional contact of the bobbin and must therefore be solidly stacked. Temperature variations, particularly in service when the windings carry current may cause expansion of the bobbin body, allowing loosening of the core members. Among these, the "I" laminations have no other support than lateral pressure; consequently, some may fall out.
U.S. Pat. No. 3,644,156 discloses a method of assembly of bobbins of various sizes wherein the flange members form no integral part of the tubular portion over which the wires are to be wound. A solid guide form is used, accepting various desired lengths of bobbin sleeves, the flanges being then placed over the particular length of sleeves chosen to complete the structure. In this type of manufacture, the selection of the lengths of the sleeves and their assembly over the guide member is, of course, time consuming and involves glueing of the assembled parts.
Aside from such labor, the ferromagnetic laminations have no retention means and must be held together either by bindings or metal frame clamping.